1. Technical Field of the Invention
The present invention relates in general to the wireless communications field and, in particular, to a short-range radio transceiver fabricated on an integrated circuit chip.
2. Description of Related Art
The high level of circuit integration possible with modern technology has allowed manufacturers of hand-held communications equipment (e.g., cellular phones) to substantially reduce the size of their products. As a general rule, these smaller products consume less power and ultimately become cheaper to produce.
In the past, there have been a number of attempts to fabricate an entire radio transmitter/receiver (transceiver) on a single integrated circuit (IC) chip. Generally, these attempts have been unsuccessful, and only parts of such radios have been placed on a single chip. For example, U.S. Pat. No. 5,428,835 to Okanobu discloses a receiver circuit formed on a single semiconductor chip. The primary reason for this lack of total integration can be found in the radio system specifications.
Most standard air interface specifications for radio communications systems set forth high requirements with respect to frequency accuracy, adjacent channel interference, modulation performance, etc. However, existing on-chip signal processing techniques have not yet reached a level that can meet the performance criteria set by these air interface specifications.
It is an object of the present invention to significantly reduce the overall size of a radio transceiver.
It is another object of the present invention to produce a short-range wireless radio link that is less costly than a cable link.
It is yet another object of the present invention to produce a short-range radio transceiver on a single integrated circuit chip.
In accordance with the present invention, the foregoing and other objects are achieved by a radio transceiver architecture that can be completely integrated into one semiconductor IC chip. In order to integrate the transceiver""s IF filters into the chip, a heterodyne architecture with a relatively low IF is used. A single directly modulated VCO is used for both up-conversion during transmission, and down-conversion during reception. Bondwires are used as resonators in the oscillator tank for the VCO. A time-division duplex scheme is used in the air interface to eliminate cross-talk or leakage. A Gaussian-shaped binary FSK modulation scheme is used to provide a number of other implementation advantages.